The present invention relates to communication control techniques in a wireless communication system. In particular, the present invention relates to a mobile wireless communication system using a distributed network, in which information concerning an access terminal is taken over between base station controllers, and to a communication control technique for movement between a plurality of mobile wireless communication systems.
In recent years, the use of the Internet has increased and the environment in which the Internet can be used has also been expanding. Especially, the ability to access the Internet using a mobile wireless communication equipment, such as a mobile phone, allows you to use the Internet wherever you are in the country.
As the use of the Internet increases and the environment in which the Internet can be used expands, services provided on the Internet have also been expanding. This results in technology needs and technical problems concerning the Internet access. For example, with regard to the services, for example, a higher speed in communication channels to adapt to the delivery of large-capacity applications, such as music/video, is required, and short delay/low jitter and the like are required as the problem to adapt to voice interactive communications. Also in the mobile wireless communication system, in order to satisfy these various needs, studies for high speed and wide band have been rapidly going on.
In the mobile wireless communication, since there is a limit in the available frequency resources, how to achieve high frequency-usage efficiency and high transmission speed within a limited frequency bandwidth is an essential key in achieving the system. Moreover, since a wireless access terminal moves and the radio environment always changes, it is necessary to control in response to an environmental change. If a control in response to an environmental change is not performed, a stable channel quality cannot be secured. As an index of the channel quality, a packet error rate obtained by averaging the percentage of success or failure in receiving packets that are transmitted and received within a wireless communication system is mainly used.
In order to satisfy the above-described conditions required for the wireless communication system, in a wireless communication system optimized to packets, a method of rapidly switching the transmission rate in response to the radio environment is employed. As such a method of rapidly switching the transmission rate in response to the radio environment, for example, in the case of an IxEV-DO scheme shown in 3gpp2, C. S0024B ver. 1.0, Cdma2000 High Rate Packet Data Air Interface Specification, a wireless access terminal itself determines the transmission rate based on the radio environment and the channel quality condition, and periodically reports this to a wireless base station, and communicates with this transmission rate, thereby achieving a high-speed switching.